Radiation is employed in a variety of scientific and medical applications. For example, it is well known that certain polymerization reactions may be initiated by, for example, electron beam radiation or ultraviolet radiation. Such radiation initiated polymerization reactions are most successfully employed when it is desired to polymerize relatively thin films of monomer or prepolymer. Efforts to polymerize thicker films by this method, however, are often unsuccessful. This is because the radiation directed at the upper surface of the film is absorbed by the mixture of monomer or prepolymer and the newly formed polymer at or near the upper surface of the film and is thus not available for initiating polymerization of the monomer or prepolymer in the middle and bottom layers of the film. In addition to polymerization reactions, there are many other chemical reactions, e.g. those involving the synthesis of organic compounds, which are known to be catalyzed by ultraviolet or other irradiation.
As disclosed in U.S. Pat. No. 3,683,183 (Vizzini et al), blood and lymph have been extracorporeally irradiated in order to suppress immune antibody response to transplants and in order to manage some forms of leukemia. In European Pat. application No. 107,540, filed Dec. 3, 1980 and published on June 17, 1981 as U.S. Pat. publication No. 30,364, there is disclosed a method for the reduction of the functioning lymphocyte population in the blood supply of a human subject. The disclosed method involves first withdrawing blood from the subject, then irradiating the blood with ultraviolet light in the presence of 1 nanogram to 100 micrograms/ml. of dissolved psoralen that is activated by the irradiation and forms photoadducts with DNA. The psoralen is thus bonded to the nucleic acid of the lymphocytes so that their metabolic processes are inhibited. The irradiated blood is returned to the subject.
Many prior art irradiating devices, especially those used in medical applications, are large, cumbersome to use, and expensive to produce. The method disclosed in the aforementioned European Patent Application involves the treatment of blood at an irradiation station consisting of an irradiation chamber and a radiation source. In one disclosed embodiment, the chamber comprises a coil of tubing (e.g. polyvinylchloride tubing of the kind commonly used for administering standard intravenous solutions) which has been flattened to give it the cross-sectional form of an elongated ellipse. It is stated that the highly flattened cross-section of the coil allows for good exposure of the flowing blood to the incident radiant energy. It is believed difficult and cumbersome to treat a fixed volume of liquid, like blood, with the apparatus shown in European Pat. application No. 107,540. First of all, the apparatus would appear to be characterized by high pressure drops during use. If it is desired to treat a specified volume of material and it is necessary, in order to obtain high radiation efficiency, to provide a radiation chamber of quite limited thickness or depth, then the apparatus tends to be bulky and cumbersome. The bulk of the apparatus might be reduced by increasing the thickness or depth of the radiation chamber through which the blood flows, but this approach reduces radiation efficiency due to radiation extinction. It is possible to retain the limited thickness or depth of the radiation chamber, thus maintaining radiation efficiency, and at the same time reduce the overall bulk of the apparatus; this approach, however, would necessitate an undesirable increase in the time needed to irradiate a fixed volume of material. This increased time factor is especially undesirable when extracorporeally circulating blood is being treated.